Chromatograph for determination of admixtures in gases

ABSTRACT

A chromatograph for the determination of admixtures in gases, comprises a chromatographic column bent in the form of at least a single helix coil or an arc of circle and which is rigidly secured on the shaft of a drive device in a plane perpendicular to the axis of the shaft. The shaft is mounted in stationary supports so that at the same time one portion of the chromatographic column is immersed in a refrigerant bath and the other portion of the column is in a heater, and during the rotation of the shaft said portions of the column subsequently pass through the cooling and heating zones.

United States Patent lnventors Viktor lvanovich Samuilov oblast,Leninsky Raion doma Uniigaz, 4A, Kv.59, Moskovskaya Oblsst; JuryMarkovich Genkin, ulitsa Usacheva, 62, Kv.254; Maria DmitrievnaSuvorova, Simonovsky va1., 12, Kv. 171, Moscow,

USSR. Appl. No. 744,517 Filed July 12, 1968 Patented May 18, 1971CHROMATOGRAPH FOR DETERMINATION OF 53 (C); 55/53, 67, 78, 80,197, 386,390; 23/232 (C), 254 (C), (lnquired) Primary Examiner-Richard C.Queisser Assistant ExaminerC. E. Snee, lll AttorneyWaters, Roditi &Schwartz ABSTRACT: A chromatograph for the determination of admixturesin gases, comprises a chromatographic column bent in' the form of atleast a single helix coil or an arc of circle and which is rigidlysecured on the shaft of a drive device in a plane perpendicular to theaxis of the shaft. The shaft is mounted in stationary supports so thatat the same time one portion of the chromatographic column is immersedin a refrigerant bath and the other portion of the column is in aheater, and during the rotation of the shaft said portions of the columnsubsequently pass through the cooling and heating zones.

PATENTEB m1 8 ISYI 3578" 757 sum 2 or 4 FIG. 4

PATENIED M18197:

SHEET 3 OF 4 CHROMATOGRAPH FOR DETERMINATION OF ADMIXTURES IN GASES Thisinvention relates to chromatographs for determination of gas admixtures,and can particularly be used to advantage for determination ofadmixtures in gases, boiling at low tem peratures, such as helium andneon.

Known in the art are chromatographs for determination of gas admixtures,comprising a bath filled with a refrigerant, a heater. a chromatographiccolumn in the form of a coil, and a drive unit which moves thechromatographic column in the cooling and the heating zones. Inchromatographs of this type the entire chromatographic column is firstplaced into the refrigerant bath and then into the heater.

Disadvantages of the prior art chromatographs consist in theircomplicated construction and in the requirement for a preliminarycooling of the entire chromatographic column which considerably prolongsanalytic procedure.

An object of this invention is to provide a chromatograph capable ofoperating in the continuous process stream without changing over gasstreams or electrical circuits while in operation. Another object of theinvention is to provide a chromatograph for determination of admixturesin gases which would be convenient in use and simple in construction.

With these and other objects in view, the chromatograph fordetermination of admixtures in gases comprises, according to the presentinvention, a chromatographic column which is a helical tube of at leastone coil fixedly attached to a shaft of a drive unit, said shaft beingborne in stationary supports so that one part of the column is immersedin the refrigerant in the cold bath, while the other part of the columnis in the heater zone, and during rotation of the shaft the columnpasses in turn to and from the cold and the heater zones, the shaft andstationary supports being provided with interconnected communicatingchannels for gas delivery into and discharge from the chromatographiccolumn.

The shorter time of the analysis with the present chromatograph has beenachieved due to the use of a temperature field which shifts along thesorbent bed without preliminary cooling of the entire sorbent bed.

These and other objects and advantages of the invention will be betterunderstood from the description of specific embodiments thereof and theappended drawings, in which:

FIG. 1 is a general view of the chromatograph provided by the invention,with partial cutaway;

FIG. 2 is a schematic axonometric view of the chromatograph according tothe invention;

FIG. 3 is a schematic axonometric view of an alternative modification ofthe chromatograph;

FIG. 4 is a section taken along the axis of the shaft of the drive unitof the chromatograph according to the invention;

FIG. 5 illustrates a diagram of gas flow in the chromatograph shown inFIG. 2;

FIG. 6 illustrates a gas flow diagram for the chromatograph shown inFIG. 3; and

FIG. 7 is an electrical circuit diagram of the chromatograph accordingto the invention;

FIG. 8 is atypical detector trace according to the invention.

The chromatograph according to the invention comprises a refrigerantbath I (FIGS. 1-3) and a heater 2, which ensure refrigeration andheating of the chromatographic column respectively, and achromatographic column 3, manufactured from stainless steel.

In one embodiment of the invention the chromatographic column 3 is anopen coil and is a helical tube in the other embodiment of thechromatograph as shown in FIGS. 2 and 3, respectively.

The column 3 is filled with a suitablesorbent and is intended toconcentrate and separate gas admixtures. The said column 3 is rotatablysupported due to a drive unit 4 comprising a shaft 5 home in stationarysupports 6 and 7 (FIG. 4) packed with special bushes 8 and 9, andoperatively associated with an electric motor 10 (FIGS. 2 and 3).

The chromatographic column 3 is fixedly attached to the shaft 5 with theaid of pins 11 and 12 perpendicularly to the shaft 5, so that one partof the chromatographic column is immersed into the refrigerant bath 1,while its other part is in the heater 2. As the shaft 5 rotates thecolumn parts pass in turn through the cold and warm zones. Channels 13and 14 in the shaft 5 (FIG. 4), intended to pass the analyzed gas, areconnected with the chromatographic column inlet and outlet openings bymeans of metal capillary tubes 15 and 16 (FIGS. 5,6).

The stationary supports 6 and 7 also have channels 17 and 18 (FIG. 4)which communicate with channels 13 and 14, respectively.

The packing bushes 8 and 9 manufactured of flaro-plast (fluorinatedplastic material) perform the functions of both packing glands andbearings. The packing bushes 8 and 9 are made in the form of cylinderswith conical bases.

The shaft 5 and stationary supports 6 and 7 also have cones which acceptthe cones of the bushes 8 and 9. The surfaces of the cones of thepacking bushes and their matching surfaces of the shaft 5 and of thestationary supports 6 and 7 are polished.

In order to prevent gas leakage, one stationary support 7 can be shiftedin the direction of the shaft 5 by manipulating an adjusting screw 19and a spring 20. The low coefficient of friction between metal andflaro-plast ensures rather free rotation of the shaft 5 mounting in thechromatographic column 3.

The heater 2 is a U-shaped rectangular ceramic housing. The innersurface of the housing has grooves 21 (FIGS. 2, 3) parallel to thehousing axis into which a heating element (not seen in the drawing) isplaced. An autotransforrner 22 (FIG. 7) serves to control the operationof the heater.

An electric fan 23 cools a portion of the chromatographic column 3 (FIG.2) or several portions of the chromatographic column (FIG. 3) prior totheir being immersed into the refrigerant bath 1.

The chromatograph has a special inlet device 25 for connection to thecylinder 24 (FIGS. 5 and 6) containing the analyzed gas, whichallows aquick flush required during the change of cylinders. The inlet device 25is connected with the chromatographic column through a flexible metalcapillary tube 26 and comprises a housing 27 with a coupling nut 28, acontrol valve 29, a valve 30 and a pressure gauge 31. The control valve29 maintains the preset flow rate of the gas to be analyzed, the valve30 serves for flushing the system, and the pressure gauge 31 measuresthe pressure within the gas cylinder 24.

All connections in the chromatograph are made with metal capillarytubes.

During the period between analyses, the control valves 2 and an outletvalve 32 are closed, while the system confined therebetween remainsunder the pressure of the analyzed gas. The residual pressure iscontrolled by the pressure gauge 33.

For the detection of admixtures separated from the chromatographiccolumn use is made of a detector 34 (for example, a katharometer)adapted to deliver signals of certain value (depending upon the amountof each component of the admixtures) to a recorder 35 serving to recordsaid signals on plotting paper.

The inlet unit 25 is connected by the coupling nut 28 to the cylinder 24containing helium to be analyzed and a valve v36 (FIGS. 5, 6) of thecylinder 24 and the valve 30 are opened. After the system has been giventhe required flush, the valve 30 is closed and the control valve 29 andthe outlet valve 32 are opened one after another.

From the cylinder 24, through the control valve 29 and a flexible metaltube 26, the gas is continually delivered into the comparator chamber ofthe detector 34. Further, the gas passes through the channel 17, packingbush 8, channel 13 and metal capillary tube 15, and finally enters thechromatographic column 3. From the chromatographic column 3 the gaspasses through the metal capillary tube 16, channel 14, packing bush 9and channel 18, and finally enters the working chamber of the detector34. Through the outlet valve 32 the gas is discharged from the detector34 to atmosphere. Now the following electrical connections are made: atumbler switch 37 (FIG. 7) cuts in the mains voltage, a tumbler switch38 makes the circuit of the bridge, a tumbler switch 39 starts theelectric motor 10, a tumbler switch 40 cuts in the fan 23 and a tumblerswitch 41 makes the circuit of the heater 2. The rotary motion of theelectric motor is transmitted through a reducing gear 42 (FIGS. 2, 3) toa driven gear 43 fixed on the shaft 5. By selecting a proper gear in thereducer 42, the required speed of rotation of the chromatographic column3 is obtained. The sense of rotation is opposite to the direction of thegas flow through the chromatographic column 3. Further, the bath 1 isprimed with the refrigerant-liquid nitrogenand the flow rate of theanalyzed gas is adjusted with the aid of the control valve 29 and a soapfilm flowmeter (not shown in the drawing) which is installed at thechromatograph outlet.

As the chromatographic column 3 rotates (FIGS. 2 and 5) the temperaturefield, having the gradient with an interval of from the temperature ofthe refrigerant to the sorbent regeneration temperature, moves in thedirection of the gas flow. The temperature field helps to separate andconcentrate the admixtures which separately pass to the working chamberof the detector 34, as the chromatographic column 3 outlet enters theheater 2 zone.

As the chromatographic column 3 (FIGS. 3 and 6), made in the form of ahelical tube rotates, a number of temperature fields, each having thetemperature gradient with an interval of temperatures from that of therefrigerant to the sorbent regeneration temperature, move along thesorbent bed in the direction of the gas flow. These temperature fieldsfollow one after another, their number being equal to the number of thehelix coils.

In accordance with the number of the temperature fields, the same numberof zones move along the chromatographic column 3 in which the admixturesare separated and concentrated. The amount of admixtures accumulated ineach zone, corresponds to the number of admixtures contained in thatpart of the gas which enters the chromatographic column 3 during onecomplete revolution.

Considering a specific case of analysis, let a gas, for example, heliumcontaining microadmixture of neon, oxygen, nitrogen and methane becontinuously passed through the chromatographic column 3 in a directionopposite to that of the column rotation.

The chromatographic column 3 rotates continuously within the cooling andheating zones. At the same time, along the bed of sorbent, there ismoved a temperature field with a temperature gradient ranging from minus196 C. to 350 C. (when using liquid nitrogen as refrigerant).

The direction of motion of the temperature field and the decrease oftemperature inside the latter (from plus 350 to minus 196 C.) coincideswith the direction of flow of gas under analysis, however, the rate ofthe gas flow is in all cases higher than that of the temperature fielddisplacement and depends upon the desired sensitivity of the instrument.

With an appropriate type of sorbent, rate of gas flow and rate of thecolumn rotation, the bulk of the gas being analyzed, in this particularcase, helium, will freely pass through the bed of sorbent in thetemperature field, while admixtures will be entrapped by the sorbent attheir characteristic temperatures and will concentrate in certain zonescorresponding to various components of the admixture.

Those zones occupy certain portions of the temperature field (dependingupon the admixture properties), are immovable with respect to therefrigerant bath 1 and the heater 2 and move on the bed of sorbentduring rotation of the column 3.

Thus, during the whole period of one complete revolution of the column3, there will be taking place the concentration of the admixturecomponents in said zones and, at the moment the outlet of the column 3passes through said zones, all the components will separately pass tothe recording instrument 34, that is, the full cycle of analyzing allthe admixtures takes place during one revolution of the column 3. Thechromatogram of an analysis of admixtures in helium is merely an examplepresented for clarifying the mode of the chromatograph operation.

The above is equally true both for chromatographs with a column in theform of an arc of a circle or a single helix coil, and forchromatographs with a column made as several helix coils.

The coils following the first one serve to make up for a possiblepassage of admixture components through the bed of sorbent in thetemperature field, for when a component passes through the bed ofsorbent in the first temperature field, it get to the bed of sorbent inthe second temperature field.

The first results of the analysis may be read from the instrument afterthe chromatographic column 3 completes the number of revolutions equalto that of the helix coils. Then the readings can be obtained after eachrevolution, as the chromatographic column 3 outlet enters the heater 2zone.

Before the chromatograph is taken out of operation, the refrigerant isdischarged from the bath 1, then the outlet valve 32, control valve 29,and valve 36 of the cylinder 24 are closed one after another. Finally,tumbler switches 37, 38, 39, 40 and 41 are turned off.

The present chromatograph automatically determines admixtures inlow-boiling gases, for example in helium. No pure carrier gas isrequired for the analysis. The chromatograph is free from disadvantagesinherent in the prior art instruments of the same kind, in which gassampling is employed. The chromatograph may operate in the continuousprocess stream without changing over gas streams or electrical circuits.Results of the analyses are recorded on a paper chart at 6 minuteintervals.

While a specific embodiment of the chromatograph has been disclosed inthe description, it will be understood that various modifications andchanges within the spirit of the invention may occur to those skilled inthe art. Those modifications and changes are considered to be fallingwithin the scope of the invention as set forth in the appended claims.

We claim:

1. A chromatograph for the determination of admixtures in gases, saidchromatograph comprising a chromatographic column for receiving a gas tobe analyzed, refrigerant means and heater means spaced proximate oneanother for constituting cooling and heating zones respectively, saidchromatographic column being rotatably supported and interposed betweensaid cooling and heating zones such that one portion of saidchromatographic column is within said cooling zone and a further portionthereof is within said heating zone, drive means connected to saidchromatographic column for imparting rotation thereto to thereby passsuccessive portions of said chromatographic column between said zones,said chromatographic column including at least a single coil having aninlet for receiving said gas to be analyzed and an outlet fordischarging said gas, support means for rotatably supporting said coil,said support means being provided with an inlet channel and an outletchannel communicating with said inlet and outlet of said coilrespectively, detector means connected to said outlet of said supportmeans, and recorder means connected to said detector means for receivingsignals therefrom,

said signals indicating the amount of admixtures in said gas beinganalyzed.

2. A chromatograph as claimed in claim 1, wherein said coil issubstantially circular.

3. A chromatograph as claimed in claim 1, wherein said coil is helical.

4. A chromatograph as claimed in claim 1, wherein said support meansincludes a shaft to which said chromatographic column is fixedlyconnected, and stationary end supports, said shaft including oppositeend portions rotatably supported one in one of each of said endsupports, said inlet and outlet channels of said support means extendingrespectively from a respective one of said end supports to said shaft.

5. A chromatograph as claimed in claim 1, wherein said heater meansincludes a substantially U-shaped member embracing said coil.

6. A chromatograph as claimed in claim 1, wherein said refrigerant meansincludes a liquid refrigerant bath wherein said coil is immersed.

2. A chromatograph as claimed in claim 1, wherein said coil issubstantially circular.
 3. A chromatograph as claimed in claim 1,wherein said coil is helical.
 4. A chromatograph as claimed in claim 1,wherein said support means includes a shaft to which saidchromatographic column is fixedly connected, and stationary endsupports, said shaft including opposite end portions rotatably supportedone in one of each of said end supports, said inlet and outlet channelsof said support means extending respectively from a respective one ofsaid end supports to said shaft.
 5. A chromatograph as claimed in claim1, wherein said heater means includes a substantially U-shaped memberembracing said coil.
 6. A chromatograph as claimed in claim 1, whereinsaid refrigerant means includes a liquid refrigerant bath wherein saidcoil is immersed.